ASVAB Mechanical Comprehension 5 — Questions and Answers
Question 1: A bicycle shifts to a smaller rear sprocket. What is the effect on pedaling effort and speed?
- Less effort, less speed
- More effort, more speed (Correct answer)
- Less effort, more speed
- More effort, less speed
Correct answer: More effort, more speed
A smaller rear sprocket increases the gear ratio, requiring more force to pedal but producing higher wheel speed.
Question 2: Which type of stress acts parallel to the cross-section of a material, causing layers to slide?
- Tensile stress
- Compressive stress
- Shear stress (Correct answer)
- Bending stress
Correct answer: Shear stress
Shear stress acts parallel to a surface, causing adjacent material layers to slide relative to each other.
Question 3: A flywheel stores energy by using its:
- Magnetic field
- Rotational inertia (Correct answer)
- Spring constant
- Thermal mass
Correct answer: Rotational inertia
A flywheel stores kinetic energy as rotational inertia, resisting changes in angular velocity.
Question 4: If you double the diameter of a pipe while keeping flow velocity constant, how does the flow rate change?
- It doubles
- It triples
- It quadruples (Correct answer)
- It stays the same
Correct answer: It quadruples
Flow rate = area × velocity; doubling diameter quadruples area (πr²), so flow rate quadruples.
Question 5: A ratchet mechanism allows motion in one direction only. What component prevents reverse rotation?
- Bearing
- Detent pawl (Correct answer)
- Worm gear
- Cam follower
Correct answer: Detent pawl
The pawl engages the ratchet wheel's teeth to block rotation in the reverse direction.
Question 6: Which of the following increases the resonant frequency of a vibrating mechanical system?
- Increasing mass
- Decreasing spring stiffness
- Increasing spring stiffness (Correct answer)
- Adding damping
Correct answer: Increasing spring stiffness
Resonant frequency = √(k/m); increasing spring stiffness k raises the resonant frequency.
Question 7: Two parallel beams of the same material and length support the same load. Beam A has twice the cross-sectional area of Beam B. Which statement is true?
- Beam A deflects twice as much
- Beam B deflects twice as much (Correct answer)
- Both deflect equally
- Beam A deflects four times as much
Correct answer: Beam B deflects twice as much
Greater cross-sectional area gives higher moment of inertia and stiffness, so the smaller Beam B deflects more.
ASVAB Mechanical Comprehension 5
A bicycle shifts to a smaller rear sprocket.
What is the effect on pedaling effort and speed?